Re: [PATCH v7 02/11] rcu: Make call_rcu() lazy to save power

[Paul E. McKenney]

On Tue, Oct 04, 2022 at 01:41:38PM +0200, Uladzislau Rezki wrote:
> >  		trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("Check"));
> >  		rcu_nocb_lock_irqsave(rdp, flags);
> >  		lockdep_assert_held(&rdp->nocb_lock);
> >  		bypass_ncbs = rcu_cblist_n_cbs(&rdp->nocb_bypass);
> > -		if (bypass_ncbs &&
> > +		lazy_ncbs = READ_ONCE(rdp->lazy_len);
> > +
> > +		if (bypass_ncbs && (lazy_ncbs == bypass_ncbs) &&
> > +		    (time_after(j, READ_ONCE(rdp->nocb_bypass_first) + jiffies_till_flush) ||
> > +		     bypass_ncbs > 2 * qhimark)) {
> Do you know why we want double "qhimark" threshold? It is not only this
> place, there are several. I am asking because it is not expected by the
> user.

OK, I will bite...  What does the user expect?  Or, perhaps a better
question, how is this choice causing the user problems?

							Thanx, Paul